Question

我有一个带有struct的表销售订单：

- ItemID
- Customer
- Year
- Month
- Quantity

我想要构建报告，如：

Customer | Item  | Year | Month | Quantity | The same month of the previous year quantity|

你能帮我吗？感谢。

Answer 1

您可以通过执行SELF JOIN并加入前一年来完成此操作：

SELECT 
T1.Customer,
T1.Item,
T1.Year,
T1.Month,
T1.Quantity,
T2.Quantity AS Last_year_quantity
FROM Table AS T1
LEFT JOIN Table AS T2 ON T1.Customer=T2.Customer 
AND T1.Item=T2.Item
AND (T1.Year-1)=T2.Year
AND T1.Month=T2.Month;

Answer 2

就像一个没有表结构或任何东西的快速模型

select a.customer, a.item, a.year, a.month, a.quantity,
  (select b.quantity 
     from table_name b 
    where b.customer = a.customer
      and b.item = a.item
      and b.month = a.month
      and b.year = a.year - 1) as prev_year_qty
from table_name a

如何在一个表中按月与另一年的数据进行比较

2 个答案: